This week marks the third anniversary of the 7 July London bombings, when 52 people were killed by suicide bombers. Wessely said evidence from past traumatic events, such as The Blitz and the 9/11 terror attacks, found that people were far more resilient than first thought during adversity.

Many businesses offer immediate counselling to staff as part of their response to traumatic events, such as police officers involved in firearms incidents or nurses who experience workplace violence. Employers also believe that interventions will reduce their exposure to litigation.

But Wessely warned that so-called ‘psychological debriefing’ was at best ineffective and at worst harmful. Giving automatic leave from work was also not helpful, he said, as attending work and being with colleagues can actually help alleviate stress.

“The process of debriefing, part of which is to warn participants of emotional reactions that might be expected to develop over weeks and months, may actually increase the occurrence of these symptoms,” he said. “For some people, not talking is the most appropriate response.”

Rather than assume that people cannot cope, employers should make the opposite assumption, and only offer interventions when employees ask for help or where it is obvious they are struggling to adjust emotionally, he added.